1. Field of the Invention
The present invention relates to a projector that projects and displays color images.
2. Description of the Related Art
Liquid crystal panel projectors typically have an illumination optical system for emitting illumination light, a color light separation system for separating the illumination light into three color lights, red (R), green (G), and blue (B), three liquid crystal light valves for modulating the respective color lights in response to image information (image signals), a color light synthesizing optical system for synthesizing the three modulated color lights with one another to synthesized light, and a projection optical system for projecting the synthesized light on a screen.
A relay optical system including a lens is generally provided in at least one optical path among three optical paths of the three color lights, in order to cause the light bundles (bundles of rays) of the respective color lights entering the three liquid crystal light valves to have substantially equal sizes. The presence of the relay optical system, however, leads to color non-uniformity in the resulting color image projected and displayed on the screen.
The relay optical system converges and re-diverges the light bundle (bundle of rays) of the color light passing through the relay optical system. The relay optical system accordingly turns the cross sectional luminance distribution of the color light upside down and left-side right. In the case where the color lights emitted from the illumination optical system and illuminate the respective liquid crystal light valves have non-uniform cross sectional luminance distributions, the synthesized light, which is obtained by synthesizing the modulated color light passing through the relay optical system with the other modulated color lights not passing through the relay optical system, includes the modulated color light having the inverted cross sectional luminance distribution. This undesirably causes color non-uniformity in the resulting color image projected and displayed on the screen.
The object of the present invention is thus to provide a technique that reduces color non-uniformity in a color image projected and displayed by a projector.
At least part of the above and the other related objects is attained by a first projector that projects and displays a color image. The first projector includes: an illumination optical system that emits illumination light; a color light separation optical system that divides the illumination light emitted from the illumination optical system into first through third color lights, which respectively have three different color components; first through third electro-optical devices that respectively modulate the first through the third color lights, which are separated by the color light separation optical system, in response to first through third image signals and thereby generate first through third modulated lights; a color light synthesizing optical system that synthesizes the first through the third modulated lights with one another and emits synthesized light; a projection optical system that projects the synthesized light emitted from the color light synthesizing optical system; a relay optical system that is provided in one optical path selected out of three optical paths, which respectively connect the color light separation optical system with the first through the third electro-optical devices, the relay optical system regulating a size of a light bundle of a selected color light entering the corresponding electro-optical device; and an adjustment section that adjusts a specific image signal, which is one out of the first through the third image signals and corresponds to the electro-optical device that receives the selected color light passing through the relay optical system, a degree of the adjustment being depend on pixel positions of a color image so that cross sectional luminance distributions of the first through the third modulated lights on a light-exiting side of the color light synthesizing optical system have substantially same gradients at least when the first through the third image signals reproduce a white image.
The first projector of the present invention has the adjustment section that carries out the adjustment, so that cross sectional luminance distributions of the first through the third modulated lights on a light-exiting side of the color light synthesizing optical system have substantially same gradients at least when the first through the third image signals reproduce a white image. The adjustment section functions to reduce color non-uniformity in the white image even when the light bundle of the color light passing through the relay optical system is converged and re-diverged. This arrangement thus effectively reduces the color non-uniformity in the color image projected and displayed by the projector.
The first projector advantageously reduces the color non-uniformity by simply adjusting only one image signal corresponding to the electro-optical device that receives one color light passing through the relay optical system.
In the first projector, it is preferable that the selected color light passing through the relay optical system is a color light having the highest luminance among the first through the third color lights.
The cross sectional luminance distribution of one color light having the highest luminance is accordingly reverse both vertically and horizontally to the cross sectional luminance distributions of the two residual color lights. The arrangement substantially equalizes the luminance of each modulated color light by adjusting only the image signal corresponding to the electro-optical device that receives the one color light having the highest luminance. This ensures the accurate reproduction of the hue of the color image.
It is here assumed that a color light having a relatively low luminance is set to the selected color light passing through the relay optical system. In this case, the adjustment lowers the luminance of the other color lights, in order to attain the accurate reproduction of the hue of the color image. This, however, darkens the resulting image. The advantage of the above arrangement is accordingly to attain the accurate reproduction of the hue of the color image without significantly lowering the brightness of the image.
The present invention is also directed to a second projector that projects and displays a color image. The second projector includes: an illumination optical system that emits illumination light; a color light separation optical system that divides the illumination light emitted from the illumination optical system into first through third color lights, which respectively have three different color components; first through third electro-optical devices that respectively modulate the first through the third color lights, which are separated by the color light separation optical system, in response to first through third image signals and thereby generate first through third modulated lights; a color light synthesizing optical system that synthesizes the first through the third modulated lights with one another and emits synthesized light; a projection optical system that projects the synthesized light emitted from the color light synthesizing optical system; a relay optical system that is provided in one optical path selected out of three optical paths, which respectively connect the color light separation optical system with the first through the third electro-optical devices, the relay optical system regulating a size of a light bundle of a selected color light entering the corresponding electro-optical device; and an adjustment section that adjusts specific image signals, which are two out of the first through the third image signals and correspond to the electro-optical devices that receive two residual color lights not passing through the relay optical system, a degree of the adjustment being depend on pixel positions of a color image so that cross sectional luminance distributions of the first through the third modulated lights on a light-exiting side of the color light synthesizing optical system have substantially same gradients at least when the first through the third image signals reproduce a white image.
The second projector of the present invention exerts the similar functions and advantages to those of the first projector discussed above. This arrangement reduces color non-uniformity in the white image even when the light bundle of the color light passing through the relay optical system is converged and re-diverged, thus effectively reducing the color non-uniformity in the color image projected and displayed by the projector.
The present invention is further directed to a third projector that projects and displays a color image. The third projector includes: an illumination optical system that emits illumination light; a color light separation optical system that divides the illumination light emitted from the illumination optical system into first through third color lights, which respectively have three different color components; first through third electro-optical devices that respectively modulate the first through the third color lights, which are separated by the color light separation optical system, in response to first through third image signals and thereby generate first through third modulated lights; a color light synthesizing optical system that synthesizes the first through the third modulated lights with one another and emits synthesized light; a projection optical system that projects the synthesized light emitted from the color light synthesizing optical system; relay optical systems that are respectively provided in two optical paths selected out of three optical paths, which respectively connect the color light separation optical system with the first through the third electro-optical devices, each relay optical system regulating a size of a light bundle of a selected color light entering the corresponding electro-optical device; and an adjustment section that adjusts a specific image signal, which is one out of the first through the third image signals and corresponds to the electro-optical device that receives one residual color light not passing through the relay optical system, a degree of the adjustment being depend on pixel positions of a color image so that cross sectional luminance distributions of the first through the third modulated lights on a light-exiting side of the color light synthesizing optical system have substantially same gradients at least when the first through the third image signals reproduce a white image.
The third projector of the present invention exerts the similar functions and advantages to those of the first projector discussed above. This arrangement reduces color non-uniformity in the white image even when the light bundle of the color light passing through the relay optical system is converged and re-diverged, thus effectively reducing the color non-uniformity in the color image projected and displayed by the projector.
The third projector advantageously reduces the color non-uniformity by simply adjusting only one image signal corresponding to the electro-optical device that receives one color light not passing through the relay optical system.
The present invention is also directed to a fourth projector that projects and displays a color image. The fourth projector includes: an illumination optical system that emits illumination light; a color light separation optical system that divides the illumination light emitted from the illumination optical system into first through third color lights, which respectively have three different color components; first through third electro-optical devices that respectively modulate the first through the third color lights, which are separated by the color light separation optical system, in response to first through third image signals and thereby generate first through third modulated lights; a color light synthesizing optical system that synthesizes the first through the third modulated lights with one another and emits synthesized light; a projection optical system that projects the synthesized light emitted from the color light synthesizing optical system; relay optical systems that are respectively provided in two optical paths selected out of three optical paths, which respectively connect the color light separation optical system with the first through the third electro-optical devices, each relay optical system regulating a size of a light bundle of a selected color light entering the corresponding electro-optical device; and an adjustment section that adjusts specific image signals, which are two out of the first through the third image signals and correspond to the electro-optical devices that receive the two selected color lights passing through the relay optical systems, a degree of the adjustment being depend on pixel positions of a color image so that cross sectional luminance distributions of the first through the third modulated lights on a light-exiting side of the color light synthesizing optical system have substantially same gradients at least when the first through the third image signals reproduce a white image.
The fourth projector of the present invention exerts the similar functions and advantages to those of the first projector discussed above. This arrangement reduces color non-uniformity in the white image even when the light bundle of the color light passing through the relay optical system is converged and re-diverged, thus effectively reducing the color non-uniformity in the color image projected and displayed by the projector.
In any of the first through the fourth projectors discussed above, the adjustment section may carry out the adjustment according to the pixel positions of an image only when values of pixels constituting the specific image signal of interest are within a preset range of relatively high luminance.
This arrangement reduces the color non-uniformity in the projected and displayed image that is at least a practically white image, thus effectively reducing the color non-uniformity in the resulting color image projected and displayed by the projector.
In accordance with one preferable embodiment of any of the first through the fourth projectors discussed above, the illumination optical system includes: a light source; a lens array that divides a light bundle emitted from the light source into a plurality of sub-beams; and a superimposing lens that causes the plurality of sub-beams output from the lens array to be superimposed in the first through the third electro-optical devices.
The illumination optical system of such configuration does not attain the uniform cross sectional luminance distributions of the respective color lights that illuminate the corresponding electro-optical devices. Application of the present invention thus exerts the significant advantages on the projector including this illumination optical system.
These and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments with the accompanying drawings.